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Sleep paralysis

Sleep paralysis is a temporary inability to move or speak that happens when you are waking up or, less commonly, falling asleep.

Although you are awake, your body is briefly paralysed, after which you can move and speak as normal. The paralysis can last from a few seconds to several minutes.

Sleep paralysis does not harm your body, but not being able to move can be very frightening.

Some people have sleep paralysis once or twice in their life, while others experience it a few times a month or more regularly.

Why does sleep paralysis happen?

It is normal for your muscles to be paralysed at certain times when you are asleep. Sleep paralysis occurs when the mechanism that causes your muscles to relax during sleep temporarily persists after you have woken up.

Sometimes, sleep paralysis can be a symptom of narcolepsy. Narcolepsy is a relatively rare sleep disorder that causes a person to fall asleep suddenly and unexpectedly, disrupting their normal sleep pattern.

Other risk factors for sleep paralysis include:

sleep deprivation

a possible family tendency towards the condition

Who is affected?

Sleep paralysis may affect people of any age, but it is more common in teenagers and young adults.

Estimates of the number of people affected by sleep paralysis vary, but one study found that around 6% of people will experience at least one episode of sleep paralysis in their life.

Outlook

Sleep paralysis does not affect your general physical health and the symptoms can often be improved by improving your sleep habits and sleeping environment.

In severe cases, your GP may suggest that you try taking a certain type of antidepressant medication for a month or two, to see if this improves the condition.

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To understand what causes sleep paralysis, it is helpful to know what normally happens when you are asleep.

REM sleep

Sleep happens in cycles, each of which is split into two phases: non-REM and REM sleep. REM stands for rapid eye movement, as the eyes dart around during this stage.

The brain is very active in REM sleep and most dreams occur during this period. Also during this time, the body is paralysed, apart from the eyes and diaphragm (the main muscle used in breathing). It is thought that this occurs to stop us acting out the actions in our dreams.

Sleep paralysis happens when the normal muscular paralysis of REM sleep temporarily continues after you have woken up.

Risk factors

Certain factors make you more likely to get sleep paralysis:

sleep deprivation - sleep paralysis is more common in people who do not get enough sleep

irregular sleeping patterns - people with irregular schedules or who do shift work are more prone to sleep paralysis

age - it is more common in teenagers and young adults

narcolepsy - some people who have narcolepsy, a sleep disorder, also experience sleep paralysis

genetic link - sleep paralysis may have a family link, although this theory needs more research

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Improving sleeping habits

Sleep paralysis is more common in people who are sleep deprived, so getting enough sleep could reduce the number of episodes of sleep paralysis you have. Most adults need around six to nine hours of sleep each night.

Keeping a regular sleeping schedule, where you go to bed and get up at roughly the same time, can also help.

Tips for improving your sleeping habits include:

creating a restful sleeping environment that is quiet, dark and not too hot or cold

making sure your bed is comfortable

exercising regularly, but not close to bedtime

cutting down on caffeine

not eating or drinking alcohol before bedtime

not smoking, as nicotine is a stimulant

Medication

If your sleep paralysis is particularly troublesome, you may be prescribed a short course of medication called a tricyclic antidepressant, such as clomipramine. Antidepressants are most commonly used to treat depression, but they can also treat severe sleep paralysis.

The medication works by altering the depth of REM sleep. This should stop the temporary paralysis when you wake up or fall asleep, and should also reduce the number of any hallucinations you have. The medication may be taken for a month or two to see if it improves your symptoms.

Tricyclic antidepressants are not addictive. Side effects of this type of antidepressant can include:

constipation

difficulty urinating

blurred vision

dry mouth

weight gain or weight loss

drowsiness

sweating

lightheadedness

skin rash

Contact your GP if these side effects do not ease within 7 to 10 days after starting the treatment.

Narcolepsy

Sometimes, sleep paralysis can be a symptom of the disorder narcolepsy, which causes sudden, unexpected "sleep attacks".